We have demonstrated in 10 normal subjects that breathing a He (80%) O2 (20%) mixture has no significant effect on static lung pressure volume behavior. Partial flow volume (FV) curves were found to be superior to full FV curves in detecting response to bronchodilator in 49 subjects with respiratory symptoms. In 15 of 30 patients with significant reduction in expiratory flow we found normal density dependence comparing air and HeO2 FV curves at 50% VC. No subject had asthma. The response to bronchodilator appears predictable based on control level of density dependence. In autopsy human lungs we have been moderately successful in predicting the FV curve from measures of airway pressure-area behavior and static pressure volume curves. Normal values for total respiratory resistance at an oscillation frequency of 3 cps have been established. BIBLIOGRAPHIC REFERENCES: Rodarte, J.R., Hyatt, R.E. and Westbrook, P.R.: Determination of Lung Volume by Single and Multiple Breath Nitrogen Washout. Amer. Rev. Resp. Dis. 114:131, 1976. Frazier, A.R., Rehder, K., Sessler, A.D., Rodarte, J.R. and Hyatt, R.E.: Single Breath Oxygen Tests for Individual Lungs in Awake Man. J. Appl. Physiol. 40:305, 1976.